U0101
High SeverityLost Communication with TCM
Network/Communication System
U0101 — Instant Answer
Lost Communication with TCM
Severity: HIGH SEVERITY
Meaning: Communication lost between the ECM and transmission control module.
Safe to drive? NO if CEL is flashing. YES with caution if solid, but repair this week.
Estimated repair cost: $0 - $600
Most common causes:
- 1. CAN bus wiring fault (35-45% of cases)
- 2. Failed TCM (10-25% of cases)
- 3. TCM fuse blown (10-25% of cases)
Symptoms
- ⚠️Transmission warning light
- ⚠️No shifting or limp mode
- ⚠️Check engine light
- ⚠️Multiple codes
Related Symptoms
Common Causes
How to Diagnose U0101
- 1Check TCM fuses
- 2Inspect CAN bus wiring
- 3Check TCM connectors
OEM Procedures for U0101
U0101 affects the Engine Control Module. Found 146 OEM service manual procedures.
12 90 120 Removing and installing/replacing control unit bracket (Cooper 4-door hatchback, Cooper 2-door hatchback, 2020-2023) - Replacement: Remount DME control unit and the integrated supply module (PDM)
12 90 120 Removing and installing/replacing control unit bracket (Cooper 4-door hatchback, Cooper 2-door hatchback, 2020-2023) - Replacement: Remount DME control unit and the integrated supply module (PDM)
12 90 120 Removing and installing/replacing control unit bracket (Cooper 4-door hatchback, Cooper 2-door hatchback, 2020-2023) - Replacement: Remount DME control unit and the integrated supply module (PDM)
12 90 120 Removing and installing/replacing control unit bracket (Cooper 4-door hatchback, Cooper 2-door hatchback, 2020-2023) - Replacement: Remount DME control unit and the integrated supply module (PDM)
12 90 120 Removing and installing/replacing control unit bracket (Cooper 4-door hatchback, Cooper 2-door hatchback, 2020-2023) - Replacement: Remount DME control unit and the integrated supply module (PDM)
12 90 120 Removing and installing/replacing control unit bracket (Cooper 4-door hatchback, Cooper 2-door hatchback, 2020-2023) - Replacement: Remount DME control unit and the integrated supply module (PDM)
12 90 120 Removing and installing/replacing control unit bracket (Cooper 4-door hatchback, Cooper 2-door hatchback, 2020-2023) - Replacement: Remount DME control unit and the integrated supply module (PDM)
12 90 120 Removing and installing/replacing control unit bracket (Cooper 4-door hatchback, Cooper 2-door hatchback, 2020-2023) - Replacement: Remount DME control unit and the integrated supply module (PDM)
Showing 8 of 146 procedures
OEM Diagnostic Flowchart
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U0101 requires a scanner that reads network modules — basic code readers won't see it.
ArtiLink600
$99
DIYers working on ABS/airbag systems
View on TOPDON
ArtiDiag900 Lite
$299.24
Serious DIYers and side-hustle mechanics
View on TOPDONGot a repair estimate for U0101? Check if the quote is fair before ordering parts.
Parts & Tools for This Job
Common parts shoppers buy for U0101 Lost Communication with TCM.
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OBD2 scanner
Read codes and freeze-frame data before you guess at the fault.
Most diagnostic jobs start with a scan tool and a verified code path.
Check SpecificationsBattery tester
Check cranking and charging health before replacing expensive parts.
A weak battery can mimic alternator or starter problems.
Check SpecificationsMultimeter kit
Confirm voltage, continuity, and sensor power with one simple kit.
A meter is the cheapest way to rule out a bad circuit fast.
Check SpecificationsRelated Resources
Repair guides, symptom pages, and wiring diagrams related to U0101.
OEM Manual Evidence
Browse →Loss of Communication DTC Cross-Reference Chart — 2013 Acura ILX Base, 2.0L Eng VIN 1 Service Manual ~ LEMON Manuals LEMON Manuals: Repair...
Tire Pressure Monitoring System (TPMS) DTCS (2016 2017 2018 2019 2020 2021 2022) — 2013 Acura ILX Base, 2.0L Eng VIN 1 Service Manual ~ LEM...
Driving Support DTCS (2016 2017 2018 2019 2020 2021 2022) — 2013 Acura ILX Base, 2.0L Eng VIN 1 Service Manual ~ LEMON Manuals LEMON Manual...
Driving Support DTCS (2016 2017 2018 2019 2020 2021 2022) — 2013 Acura ILX Base, 2.4L Eng VIN 2 Service Manual ~ LEMON Manuals LEMON Manual...
Related Symptoms
Browse →Exact Vehicle Hubs
Browse →Related Codes
A module has lost CAN bus communication with the engine control module.
The TCM (Transmission Control Module) has detected a fault and sent a message to the ECM. This is a general indicator that transmission-specific codes are stored.
Frequently Asked Questions
- Will my car shift without the TCM?
- The transmission enters limp mode — usually stuck in 3rd gear. Driveable but with limited function.
- Can water damage the TCM?
- Yes — on some vehicles the TCM is mounted low and can be damaged by flooding or deep water.
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Author & Review
Published by AllOEMManuals, founded by Lyndon Bedford, an automotive technician with 20 years of experience. He owned and operated a mechanic shop in Hurst, Texas from 2014 to 2022 and continues hands-on repair work.
Content may combine manual references, general repair templates, and AI-assisted drafting. Confirm the source, vehicle configuration, and applicability before working. Report corrections through our contact page.
Last updated: 2026-11-07